Simple Samples of Java OOP 4 Principles

Inheritance

Basically it means a class extends to another class for inheritance.

class A {}
class B extends B {}

In Java, it also support multiple inheritance.

class A {}
class B {}
class C extends A, B {}

Polymorphism

Basically it is concept of overriding, overloading and assignment for a class.

class Animal {
  public void animalSound() {
    System.out.println("The animal makes a sound");
  }
}

class Pig extends Animal {
  public void animalSound() {
    System.out.println("The pig says: wee wee");
  }
}

class Dog extends Animal {
  public void animalSound() {
    System.out.println("The dog says: bow wow");
  }
}

Abstraction

We can create an abstract class without filling the detail of the function, eg abstract class or interface.

// abstract class
public abstract class A { public abstract void abstractMethod(); }
// interface I
public interface I { public void interfaceMethod(); }

Encapsulation

It is a permission control level.

// you can only access parameter "name" if you use getName() method.
public class E {
  private String name;
  public String getName {
    // passing the auth check
    return name;
  }
}

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